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The Life of a Cell
A View of the
Cell
The Discovery of
Cells
A View of a Cell
• Cells : the basic building blocks of
all living things.
Development of Light Microscopes
• The first person to record looking at water
under a microscope was Anton van
Leeuwenhoek.
• The microscope van Leeuwenhoek used is
considered a simple light microscope
because it contained one lens and used
natural light to view objects.
Development of Light Microscopes
•Compound light microscopes: use a series
of lenses to magnify objects in steps.
These
microscopes
can magnify
objects up to
1,500 times.
The Cell Theory
• Robert Hooke was an English scientist who
lived at the same time as van Leeuwenhock.
• Hooke used a compound light microscope to
study cork, the dead cells of oak bark.
The Cell Theory
• Matthais Schleiden (1838)
– Observed plants- and concluded that all
plants are made of cells.
• Theodor Schwann(1939)
– Observed animals and concluded that all
animals are made of cells.
The Cell Theory
• Rudolf Virchow - 1852
– Concluded that the nucleus was responsible for
cell division
**The cell theory is made up of three
main ideas:
All organisms are composed of one or
more cells.
The cell is the basic unit of
organization of organisms.
All cells come from preexisting
cells.
Development of Electron Microscopes
• The electron microscope was invented in the 1940s.
• This microscope
uses a beam of
electrons to
magnify
structures up to
500,000 times
their actual size.
Development of Electron Microscopes
There are two basic types of electron microscopes.
The scanning electron microscope scans the
surface of cells to learn their three dimensional
shape.
The transmission electron microscope allows
scientists to study the structures contained
within a cell.
**Two Basic Cell Types
1. Prokaryotic cells : Cells that do not
contain internal membrane-bound structures
• The cells of most unicellular organisms
such as bacteria do not have membrane
bound structures and are therefore called
prokaryotes.
7.1
**Two Basic Cell Types
2. Eukaryotic cells:
•Cells containing membrane-bound structures
• Most of the multi-cellular plants and animals
Two Basic Cell Types
•
Organelles: the membrane-bound
structures within eukaryotic cells
• Each organelle has a specific function that
contributes to cell survival.
Prokaryotic
Eukaryotic
3 Facts
3 Facts
2 Similarities
1.What is happening to the starch and the sugar?
2. What does this tell you about the membrane covering the
test tube?
The Life of a Cell
A View of the
Cell
The Plasma
Membrane
All living cells must maintain a balance
regardless of internal and external conditions.
Survival depends on the cell’s ability to
maintain the proper conditions within itself.
What is this called????
Why cells must control materials
• What helps cells control
homeostasis?
• Plasma membrane :the
boundary between the cell
and its environment.
• Selective permeability : a process used to
maintain homeostasis allowing some
molecules into the cell while keeping others
out.
It is the plasma membrane’s job to:
• allow a steady supply of glucose, amino acids,
and lipids to come into the cell no matter what
the external conditions are.
• remove excess amounts of these nutrients when
levels get so high that they are harmful.
• allow waste and other products to leave the
cell.
Plasma
Membrane
Water
Structure of the Plasma Membrane
The plasma
membrane is
composed of two
layers of
phospholipids
back-to-back.
•Phospholipids : lipids with a
phosphate attached to them.
The lipids in a
plasma membrane
have a glycerol
backbone, two
fatty acid chains,
and a phosphate
group.
Phosphate
Group
Glycerol
Backbone
Two Fatty
Acid
Chains
Makeup of the phospholipid bilayer
• The phosphate
heads are polar
and hydrophilic.
They face out.
• The fatty acid
tails are nonpolar
and hydrophobic.
They face inside
Makeup of the phospholipid bilayer
• Fluid mosaic model :
the phospholipids move
within the membrane
(waves), as well as, the
proteins in the
membrane (boats).
Components of the plasma membrane:
Cholesterol prevents the fatty acid chains of
the phospholipids from sticking together.
Cholesterol
Molecule
**Think spaghetti and butter**
Components of the plasma membrane:
• Transport proteins: move needed
substances or waste materials through the
plasma membrane.
• Other proteins and carbohydrates stick out
of the cell’s surface to identify chemical
signals.
The Life of a Cell
A View of the
Cell
The Eukaryotic
Cell
Cellular Boundaries
The plasma
membrane acts
as a selectively
permeable
membrane.
•Cell wall : rigid
structure located outside
the plasma membrane
that provides additional
support and protection.
Nucleus and cell control
•Chromatin :
are strands of
genetic
material
Nuclear
Envelope
•Nucleolus: helps
with ribosome
production
Inside the Eukaryotic Cell
•Cytoplasm: the
gelatin-like material
inside every cell; it
constantly flows
inside the cell
Assembly, Transport, and Storage
•Endoplasmic
reticulum (ER) : the
site of cellular
chemical reactions;
products are
transported through
tubules that make up
the ER
Assembly, Transport, and Storage
Endoplasmic
Reticulum (ER)
•Ribosomes : the smallest
organelles that are not
membrane bound and make
proteins
Assembly, Transport, and Storage
•Golgi Apparatus
stacked, flattened
membranes used to sort
cellular substances and
package them into
membrane bound
structures called
vesicles
**Assembly, Transport, and Storage
• What is the advantage of highly folded
membranes in cells?
– Think accordion –
• A large amount of work can be done in a small
space
Vacuoles and storage
•Vacuoles : spaces used for temporary storage of
materials.
**Notice the difference between vacuoles in plant and
animal cells.
Animal
Cell
Vacuole
Plant
Cell
Lysosomes and recycling
•Lysosomes : organelles that contain digestive
enzymes.
•digest excess or worn out organelles, food
particles, and engulfed viruses or bacteria.
Energy Transformers:
Chloroplasts and energy
•Chloroplasts : cell
organelles that capture
light energy and
produce food to store
for a later time.
Chloroplasts and energy
•The chloroplasts belongs to a group of plant
organelles called plastids, which are used for
storage.
•Chloroplasts contain green pigment called
chlorophyll. Chlorophyll traps light energy
and gives leaves and stems their green color.
Mitochondria and energy
•Mitochondria :
membrane-bound
organelles in plant and
animal cells that transform
energy for the cell.
Structures for Support and Locomotion
•Cytoskeleton : support structure composed
of microtubules and microfilaments.
Cilia and flagella
Some cell surfaces have cilia and flagella,
which are structures that aid in locomotion
or feeding. Cilia and flagella can be
distinguished by their structure and by the
nature of their action.
Cilia and flagella:
used for locomotion
•Cilia : short,
numerous, hair-like
projections that move in
a wavelike motion.
Cilia
Cilia and flagella
•Flagella : long
projections that move
in a whip-like motion.
Flagella
•Flagella and cilia are
the major means of
locomotion in
unicellular organisms.